An image sensor employing multiple arrays of photodetectors is disclosed. According to one aspect of the present invention, every two of three arrays are shielded with a non-transparent material. When charge signals are generated in the non-shielded array in response to light reflected from a scanning document illuminated by one of three colored lights, the charge signals are shifted to a next adjacent shielded array so that another set of charge signals can be generated under another one of the three colored lights. Essentially, the shielded arrays are used as buffers to separate the charge signals independently generated under three different colored lights. Subsequently, the charge signals corresponding to the same colored light can be accumulated to produce a much stronger scanning signal.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An image sensor array comprising: a number of arrays of photodetectors and interlaced by two arrays of buffers, wherein the arrays of photodetectors are sequentially exposed to a document moving across the image sensor; wherein signals generated in each of the arrays of photodetectors are sequentially shifted into the two arrays of buffers; wherein buffered signals shifted out from the two arrays of buffers are integrated with the signals generated in each of the arrays of photodetectors to produce accumulated scanning signals of the document; an array of sampling circuits, each coupled to one of the photodetectors in a last array of the arrays of photodetectors, receiving respectively the accumulated signals and converting the accumulated scanning signals into sampled pixel signals; and a multiplexer, coupled to the array of sampling circuits, sequentially outputting the sampled pixel signals.
2. The image sensor of claim 1 , wherein there are N photodetectors in each of the arrays of photodetectors, there are at least N buffers in each of the two arrays of buffers, and wherein each of the N photodetectors and two corresponding buffers respectively in the two arrays of buffers are serially connected.
3. The image sensor of claim 2 , wherein a first charge signal generated in one of the N photodetectors is shifted to a first one of the two corresponding buffers.
4. The image sensor of claim 3 , wherein a second charge signal generated in the one of the N photodetectors is shifted to the first one of the two corresponding buffers after the first charge signal is shifted from the first one of the two corresponding buffers to a second one of the two corresponding buffers.
5. The image sensor of claim 4 , wherein a third charge signal generated in the one of the N photodetectors is accumulated over a stored charge signal originally stored in and now shifted out from one of the arrays of buffers.
6. The image sensor of claim 5 , wherein the first charge signal, the second charge signal and third charge signal are respective intensity signals from three different light spectrums.
7. The image sensor of claim 6 , wherein the three different light spectrums represent red, greed and blue.
8. The image sensor of claim 6 , wherein the three different light spectrums are created as a result of three different illuminations.
9. The image sensor of claim 6 , wherein the three different illuminations are from one or more red LEDs, green LEDs and blue LEDs, powered on independently.
10. The image sensor of claim 2 , wherein each of the N buffers in each of the two arrays of buffers is a photodetector masked by a non-transparent material so that the photodetector can not be exposed to the document and is used as a temporary storage space.
11. The image sensor of claim 10 , wherein a distance between a photodetector in one of the arrays of photodetectors and a corresponding buffer in one of the two arrays of buffers is determined by a scanning resolution.
12. The image sensor of claim 1 , wherein the multiplexer is controlled by an array of shift registers corresponding to the last array of the arrays of photodetectors.
13. The image sensor of claim 12 , wherein the number of arrays of photodetectors determines how many times faster the document moves across the image sensor if the resultant scanning signals are to have a similar signal strength as the resultant scanning signals generated from only one of the arrays of photodetectors.
14. A method for generating color images, the method comprising; generating N charge signals from each of M linear sensors organized in parallel, each of the M linear sensors including N photodetectors, wherein i-th photodetector in each of the M linear sensors is serially connected, 0<i N, and wherein two of every three linear sensors in the M linear sensors are shielded with a non-transparent material so that an array of non-shielded photodetectors is positioned between first two arrays of shielded photodetectors and second two arrays of shielded photodetectors; accumulating respectively the N charge signals over N previous charge signals shifted out from one of the first two arrays of shielded photodetectors; shifting the accumulated N charge signals into one of the second two arrays of shielded photodetectors; sampling the accumulated N charge signals in parallel to produce N sampled pixel signals; and subsequently multiplexing the N sampled pixel signals to an amplifier for output.
15. The method of claim 14 , wherein the generating of the N charge signals happens successively for each of three colored lights before a document being scanned is advanced.
16. The method of claim 15 , wherein the three colored lights are turned independently so that there are three corresponding versions of the N charge signals, one for each of the three colored lights.
17. The method of claim 16 , wherein the three colored lights are red, green and blue.
18. The method of claim 15 , wherein the N charge signals and the N previous charge signal are for the each of three colored lights.
19. The method of claim 14 , wherein the accumulating respectively of the N charge signals over the N previous charge signals shifted out from one of the first two arrays of shielded photodetectors have substantially identical magnitude and reflect from a same scanning position of a document.
20. The method of claim 19 , wherein the accumulated N charge signals are as twice strong as the N charge signals.
21. The method of claim 14 , wherein the M linear sensors are integrated on a single substrate.
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December 21, 2001
July 22, 2003
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